Application Of Modified Nano-particle Black Carbon For The Remediation Of Soil Heavy Metal Pollution

With the increasing of heavy metal contamination of soil,the pollution of heavy metal in the soil has become a hot spot in current research.As we know, nano-materials has high surface area,high reactivity and strong adsorption characteristics,so it have been used for water pollution treatment,and the world take more and more attention on this technology.However,the application in the soil environmental governance,this technology have both challenging and opportunities for development。In order to enhance chemical adsorption capacity of the nano-CB, the materials ad been oxidized in this study,and characterized its basic properties such as particle size,surface area,Infrared spectrum and Zeta potential.Adsorption and desorption of Cu(â…¡) and Cd(â…¡) on commercial active carbon(CA),parent carbon black(CB),and oxidized carbon black(OCB) were studied by batch experiments.Using soil cultivation experiment,the effects of OCB amendment on bioavailability of Cu(â…¡) and Zn in soil were studied.And the influence of OCB amendment on biomass and Cu(â…¡) and Zn(â…¡) concentration of ryegrass aerial part were also studied.The main results are as follows:The particle size of CB is between 30 to 60 nanometer.Specific surface area of CB is 1259m²g^-1,is much larger than the activated carbon,which specific surface area is 765m²g^-1.After modified,the C=C and O-H functional groups increased significantly,and the O=C-OH,C-O and CNO groups are new groups by modification,and functional group of OCB became richer.OCB have negative charge and its Zeta potential decreased by-20mV to-60mV when pH increased from 3 to 8.So OCB can absorb pollutants with positive charge.The negative charge of OCB increased significantly after been oxidized,and its isoelectric point shift left, and absorption capacity of pollutants with positive charge enhanced.Adsorption isotherms of Cu(â…¡) and Cd(â…¡) on OCB and CB fit Langmuir model very well.The maximum sorption capacities of Cu(â…¡) on OCB and CA were 438 and 99 mmol kg-1,respectively;and 282 and 72 mmol kg-1 for Cd(â…¡).The sorption capacities of OCB for the two metal ions are in the order of Cu(â…¡)＞Cd(â…¡).The percentage desorption of Cu(â…¡) and Cd(â…¡) from OCB and CA depended on the quantity of initial concentration of Cu(â…¡) and Cd(â…¡) adsorbed,and Cu(â…¡) has a lower percentage desorption than Cd(â…¡).Therefore,OCB is a better material to immobilize Cu(â…¡) and Cd(â…¡) in aqueous solutions.The pH of solution had a significant effect on the adsorption of Cu(â…¡) and Cd(â…¡).In general,heavy metal adsorption is small at low pH values.At high pH values,the metal ions are completely removed.In the binary system,Cu(â…¡) and Cd(â…¡) exhibited competitive adsorption on OCB.The adsorption of Cd(â…¡) was impeded more significantly in the Presence of Cu(â…¡).Compared with control,mixed applying OCB 1%,3%,5%,could decline percentage of Cu(â…¡) to 47.26%,72.01%,80.89%respectively after 60 days cultivation.The bioavailability of Zn(â…¡) cut down to3.00%,17.71%,43.61%after 60 days cultivation.The results of packet application were no better than mixed applying and needed longer time for equilibrium.OCB amendment significantly increased biomass of ryegrass aerial part and reduced Cu(â…¡) and Zn(â…¡) concentration of it.Application of OCB reduced exchangeable and cabonate-bound Cu(â…¡I) and Zn(â…¡) in ryegrass rhizosphere soil,and the proportion of organic/sulp hide fractions increased.It has a great significance for further study of OCB in the repair of heavy metal contaminated soil to understand the mechanism of OCB to reduce the absorption of heavy metals in ryegrass.